Compute style-determined compositing reasons during recalc style

Source/core/rendering/RenderLayer.h

Index: Source/core/rendering/RenderLayer.h
diff --git a/Source/core/rendering/RenderLayer.h b/Source/core/rendering/RenderLayer.h
index cf9654aa369d9899df8cf2db658482a291ef91a7..a951b038836c19634c3e819be52ccf24381a2ce4 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -623,9 +623,10 @@ private:
     bool lostGroupedMapping() const { return m_compositingProperties.lostGroupedMapping; }
     void setLostGroupedMapping(bool b) { m_compositingProperties.lostGroupedMapping = b; }
 
-    void setCompositingReasons(CompositingReasons);
+    void setCompositingReasons(CompositingReasons, CompositingReasons mask = CompositingReasonAll);
     CompositingReasons compositingReasons() const { return m_compositingProperties.compositingReasons; }
 
+    friend class CompositingReasonFinder;

[ojan, 2014/03/21 17:12:06]

Instead of adding to the friend madness in RenderLayer, could we just make the
right things off CompositingReasonFinder public?

[abarth-chromium, 2014/03/21 17:16:13]

Sure.  Will do.

     friend class CompositedLayerMapping;
     friend class RenderLayerCompositor;
     friend class RenderLayerModelObject;